P87C660X2 PHILIPS [NXP Semiconductors], P87C660X2 Datasheet - Page 66

• Manufacturer Part Number: P87C660X2
• Description: 80C51 8-bit microcontroller family
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
Reduced EMI Mode
The AO bit (AUXR.0) in the AUXR register when set disables the
ALE output unless the CPU needs to perform an off-chip memory
access.
Reduced EMI Mode
AUXR (8EH)
AUXR.0
See more detailed description in Figure 48.
Dual DPTR
The dual DPTR structure (see Figure 34) is a way by which the chip
will specify the address of an external data memory location. There
are two 16-bit DPTR registers that address the external memory,
and a single bit called DPS = AUXR1/bit0 that allows the program
code to switch between them.
AUXR1 (A2H)
Where:
The DPS bit status should be saved by software when switching
between DPTR0 and DPTR1.
2003 Oct 02
New Register Name: AUXR1#
SFR Address: A2H
Reset Value: xxxxxxx0B
DPS = AUXR1/bit0 = Switches between DPTR0 and DPTR1.
80C51 8-bit microcontroller family
RAM, low voltage (2.7 to 5.5 V), low power, high speed (30/33
MHz), two 400KB I
7
–
7
–
6
–
6
–
Select Reg
DPTR0
DPTR1
AO
SRD
5
5
–
2
C interfaces
LPEP
4
–
4
Fast/
STD
I
2
3
GPS
C
3
2
–
16 KB OTP/ROM, 512B
2
0
DPS
0
1
EXTRAM
1
1
–
DPS
AO
0
0
66
The GF2 bit is a general purpose user-defined flag. Note that bit 2 is
not writable and is always read as a zero. This allows the DPS bit to
be quickly toggled simply by executing an INC AUXR1 instruction
without affecting the GF2 bit.
DPTR Instructions
The instructions that refer to DPTR refer to the data pointer that is
currently selected using the AUXR1/bit 0 register. The six
instructions that use the DPTR are as follows:
The data pointer can be accessed on a byte-by-byte basis by
specifying the LOW or HIGH byte in an instruction which accesses
the SFRs. See Application Note AN458 for more details.
INC DPTR
MOV DPTR, #data16
MOV A, @ A+DPTR
MOVX A, @ DPTR
MOVX @ DPTR , A
JMP @ A + DPTR
AUXR1
DPS
BIT0
(83H)
DPH
Increments the data pointer by 1
Loads the DPTR with a 16-bit constant
Move code byte relative to DPTR to ACC
Move external RAM (16-bit address) to
ACC
Move ACC to external RAM (16-bit
address)
Jump indirect relative to DPTR
Figure 34.
(82H)
DPL
P8xC660X2/661X2
DPTR1
DPTR0
EXTERNAL
MEMORY
DATA
Product data
SU00745A